This invention relates to a solid electrolytic capacitor and a method of forming the same.
Recent development has been directed to a solid electrolytic capacitor that comprises a conductive polymer layer as a solid electrolytic. For example, a solid electrolytic capacitor with conductive polymer is disclosed in U.S. Pat. No. 7,268,997 B2, the contents of which are incorporated herein by reference. Specifically, the disclosed solid electrolytic capacitor comprises a complex conductive polymer film; the complex conductive polymer consists of an inner conductive polymer film formed on an anodized film and an outer conductive polymer film formed on the inner conductive polymer film.
Various methods has been proposed for forming a conductive polymer film, especially, based on 3,4-ethylenedioxythiophene (EDOT) monomer. For example, methods for forming a conductive polymer film based on EDOT monomers are disclosed in U.S. Pat. Nos. 4,910,645, 4,959,430, 4,987,042, 5,035,926, EP 0440957B1, U.S. Pat. No. 4,780,796 and JP_A 2002-60736, the contents of those documents being incorporated herein by reference.
However, conductive polymer films formed in accordance with the above-listed methods are insufficient in conductivity. There is a need for a conductive polymer film with high conductivity and, in particular, to a conductive polymer film that, when used in a solid electrolytic capacitor, does not heighten an ESR value of the capacitor even at a high temperature of, for example, 100° C. or more.